1. Field of the Invention
Use of an inert gas bubble-actuated molten metal pump to convey hotter molten metal and thereby assist in rapid melting of metal chips introduced into cooler molten metal in a metal-melting furnace and, in combination with a heat-and flame-resistant cover, simultaneously to provide a non-oxidizing atmosphere at the surface of the molten metal mass, thereby also to attain maximum economic utilization of the inert gas.
2. Prior Art
The state of the art regarding the introduction of metal chips into the charge well of a metal melting furnace and the conveyance of molten metal from one place to another within or out of a metal melting furnace has been fully reviewed in my prior U.S. patents, namely, U.S. Pat. Nos. 4,702,768, 4,710,126, 4,721,457, 4,872,907, 5,211,744, 5,203,910, 5,403,381, 5,468,280 and 5,407,462, the disclosures of which patents are incorporated herein by reference.
In particular, the employment of an inert gas bubble-actuated molten metal pump for moving molten metal from one place to another in a metal-melting furnace or out of a metal melting furnace has been disclosed in my prior U.S. Pat. No. 5,203,910 as well as in my U.S. Pat. Nos. 5,403,381 and 5,468,280. A heat- and flame-resistant cover for at least a substantial portion of a charge well has been disclosed in my U.S. Pat. No. 5,211,744. Various methods and charger means for introducing metal chips into the charge well of a metal-melting furnace have been disclosed in my prior U.S. Patents, in particular a stripforming briquetter device and method in my prior U.S. Pat. No. 4,702,768, a compacting extruder method and means in my prior U.S. Pat. No. 4,872,907, and a mass flow gravity feed method and apparatus for charging metal chips into the charge well of a metal-melting furnace in my prior U.S. Pat. No. 5,407,462.
Although the inventions of these prior patents have gone far in advancing the state of the art, including the efficiency of charging metal chips into the charge well of a metal-melting furnace and the conveyance of molten metal from one place to another in a metal melting furnace or out of the metal-melting furnace, an improvement in the efficiency is always a highly-desirable objective and one which is fulfilled admirably by the provision of the present invention whereby certain of the salient features of my prior inventions and patents are combined in a manner which minimizes unnecessary losses of inert gas employed in the inert gas bubble-actuated molten metal pump, utilizes the temperature gradient between different sections of a metal-melting furnace together with such an inert gas bubble-actuated molten metal pump to assist in the more rapid melting of metal chips charged into the charge well of a metal-melting furnace and into the molten metal mass therein, and at the same time utilizes the propellant or actuator inert gas from the inert gas bubble-actuated molten metal pump, in combination with a heat-resistant and flame-resistant cover over at least a substantial portion of the surface of the molten metal mass in a charge well, to capture the inert gas used as actuator beneath such a cover at the surface of the molten metal mass in the charge well, the combination of the various aspects of the invention as set forth hereinbefore increasing greatly the efficiency of the operation by an astute combination of the heat gradient between wells, the pump, the inert gas bubbles actuating the pump, and the cover, all together contributing to elevate the efficiency and economy of the operation to new and previously unattainable heights.
It goes without saying that it is not essential that the hotter molten metal be conveyed from an adjacent well into a charge well of a metal-melting furnace, so long as hotter molten metal is conveyed from one section of the metal melting furnace into a second section of the metal melting furnace containing cooler molten metal into which a new charge of chips is being introduced, and it should be clear that these two (2) sections could involve two (2) separate wells of the furnace or be present in the same well of the metal-melting furnace.
As used herein, the term "actuated", with reference to the inert gas bubble "actuated" molten metal pump, means that the pump is put into action by the inert gas. Synonymously, the pump could be said to be driven, propelled, or powered by the inert gas bubbles.